Field of Invention
Some embodiments of the present invention generally relate to lighting systems. More specifically, some embodiments of the present invention relate to LED and other solid-state lighting fixtures and devices.
Background
Lighting needs for sports can vary based on usage. Lighting levels for broadcasting may need to be 50-100% higher than for practice or for non-broadcast games. Thus lighting levels that are quite adequate for play may be insufficient for television broadcasting; this can be true even if players and spectators are completely satisfied with the lower, non-broadcasting lighting level and even if they do not perceive an improvement in lighting at the higher broadcasting level. Lighting systems therefore are normally configured for the highest lighting level required. This means that even though a field or arena may be used for practice or non-broadcast games almost all the time, and even though the need for high level lighting is typically a small fraction of the total field or arena usage, measured in tens of hours per year, the lights are operated at a high level for sometimes hundreds of hours per year. Thus if there were a way to reduce lighting levels during non-broadcast times, this could result in significant potential savings on energy usage, which could be on the order of 25-50% or more annually.
Additionally, with the adoption of LED lighting sources, further opportunities are presented relative to high intensity discharge (HID) systems, which have been the state of the art. HID systems use HID lamps (e.g. metal halide or sodium) as the light sources. HID lighting particularly does not allow much variance in lighting levels. For a nominal 1500 Watt (1500 W) HID lamp, it might exhibit a somewhat proportional relationship between power and light output from around 1300 W to around 1700 W. But as power is reduced below around 1300 W, light levels drop disproportionally with additional decreases in power. For example, the product known as MULTIWATT™ from Musco Corporation of Oskaloosa, Iowa, USA, operates a nominal 1500 W HID lamp at 1500 W for full power and at 1000 W for reduced power. See also U.S. Pat. No. 4,994,718, incorporated by reference herein. The 1000 W setting is only a 33% reduction in power but causes a 50% reduction in light output. Above the high limit (e.g. above 1500 W), light output continues to increase, but lamp longevity drops dramatically with very small additional increases in power, which normally makes increases above the high limit impractical. HID sources also have a well-known lamp lumen depreciation (LLD) characteristic. They lose light output over time of operation.
In contrast, while LEDs can exhibit similar longevity decreases above their high limit for power input, they have the potential to be dimmed to very low levels but with an increase rather than a decrease in efficiency measured in lumens/watt. Also, when LEDs are operated below their high limit, the result is typically an increase in lamp life longevity. This increase can be approximately proportional for slight decreases but can be much higher for larger decreases in operating power. LEDs also have LLD.
Further, due to the ability of LED lighting to operate at a very wide range of power levels, reducing power levels for most of the operational time could result in a reduced number of total fixtures required since fixture count would be determined by a formula based on operational hours at high power versus operational hours at lower power levels. In other words, if less lighting fixtures could supply necessary illumination levels, system costs (both capital and operating) could be reduced.
There is therefore room for improvement in the art. This includes sports lighting (indoors and outdoors) as well as analogous large or wide area lighting applications including, but not limited to, entertainment venues, parking lots, and streets and roadways, and shipping storage yards, warehouses, or any other location where desired lighting levels could vary significantly.